Sunday, February 7, 2010

The $2.99 laser trigger

(laser not included!) Its actually an IR trigger, but lasers are so much cooler! I wanted to trigger the camera to very specific action so I thought i'd get an optical trigger. There are a few commercial ones out there but as a fun hobby project (I love repurposing equpment btw) I thought this toy RC car lap timer would make for good inexpensive optical trigger. After adding a plugin jack and a diode, I had one that will trigger my pocket wizard which in turn will trigger my D300.

The lap timer is actually made for the Radio Shack ZipZap mini rc cars. They can be found for just $2.99 shipped on ebay. I comes with the lap timing scoreboard and an IR beam railing for the opposite side of the lane. two AA's power the lap timer, and 2 AAA's power the IR emitter bar. You can use the emmiter bar to make a beam for triggering. It works well but the object needs to be big enough to completely block its wide range. The laser level I'm using on the otherhand has a very tight beam, and even a single water drop passing through its path can trigger it.

While testing the stock unmodified lap timer I noticed that the Red LED on top would turn off whenever the beam was broken and be on when the IR beam was seen by the timer. So I decided to do a quick modification by adding a diode and an 1/8" (3.5mm) mono connector. That would allow it to connect to a pocket wizard transmitter.

The transmitter would trigger my DSLR with the addition of an inexpensive pre-trigger cord from Calumet (it was $9.99)

For the Canon folks...

Here it is in action, this is reject test shot that happens to show everything. You can see the laser on the right side, my water dropper in the middle, and the laser trigger on the left. The drop broke the beam, and traveled the distance seen when the camera shot it. For those needing a poor mans adjustable delay and using flash (in a dark room), one trick you can do is rear curtain sync. By syncing rear curtain you can adjust when the flash goes off, and in turn creates your exposure. If you need more discrete timing you'll have to build an adjustable delay (I've done that too, but thats another blog..)

A prettier example of it in action. using this method I can get pretty repeatable drops in front of my camera. Not the most exciting use of this trigger, but it shows it works and is repeatable.

Here is another example of the trigger, I had another photographer "spray" the camera with a card ala 52 card pickup. The laser trigger was in front of him, and I prefocused the camera so that when the cards did break the beam they would be in focus. We did a this a few times and got pretty good results, I plan on doing some more exciting triggering once things warm up and I can get outside.

All in all the trigger has been a success, it looks a little funny, but hey it cost less then a happy meal and now I can trigger things like the cool sharks in Austin Powers!


  1. Very nice!!
    That water drop shot with the duck is awesome! Love the reflection of the duck.

  2. I am curious, I found the zip-zaps unit on ebay as described, the auction had a "best offer" option, so I was able to get the price a little lower than advertised. However, I am finding that a laser is not triggering the unit... I am also wondering about the diode you used, though I am able to figure things out effectively, I am not entirely familiar with electronic diodes and their values, so knowing what voltage, amperage, and any other necessary values are required on the diode you used would be of great help.

    I am currently waiting on some 3.5mm connectors and cabling to rewire my remote shutter release and this laser trigger to be modular, and potentially interconnectable to allow for pre-trigger availability without the need for an additional cable or device. This will all be connected to my D90 and hopefully I will be able to capture some unique moments.

    Any advice you may be able to provide would be of great help. Especially with regards to the laser portion of the trigger, perhaps my laser is simply not powerful enough, or not emitting the necessary ir light. However, I did find that even from a good distance away, roughly 1.5ft, that the tip of a pen is even effective at blocking the ir transmitter....

  3. Does the IR emitting wall that came with the zipzap trigger the LED on top? Mine seemed very sensitive and when I pulled out the RED laser level it worked fine, so I can only assume theres lots of IR for the phototransistor to detect. Perhaps your laser is the problem. I used 2 different red lasers and they both worked great. I'd keep away from using a green one, it will probably fry the sensor. I've gone as far as 15-20 ft away and had plenty of light to trigger the sensor. Another note, I use this with the pocketwizards as a safety to isolate homebrew technology from my DSLR. The pocketwizard is simply looking for the grounding signal to trigger the other end where my camera is located. Cheap ebay triggers would do the same, but if you go direct I'd recommend making sure things are engineered electrically properly.

  4. Yes, the IR transmitter does trigger the LED that is on top of the base unit. Mine does not seem terribly sensitive, although, an object moving too quickly through the beam will not properly trigger the sensor. I will attempt to find an alternate laser to hopefully trigger the unit.

    With regards to wiring the unit to prevent damage to my DSLR, do you have any suggestions for wiring the unit to prevent said damage? I am concerned about the voltage that powers the LED transferring into my D90's remote port, which also happens to be the GPS add-on port. I had requested information regarding the diode you had put in place to prevent the electrical current from damaging your pocketwizard, is it possible you might be able to give me specifics regarding the voltage and amperage of the diode. I am just now delving into the area of homebrew, though repurposing is something I am somewhat familiar with. Again, any additional information you may be able to provide with regards to the electrical wiring would be appreciated, though I am primarily concerned with the diode, as I should be able to figure out the rest of the necessary information on my own.

    Thank you again,


  5. Jacob - to safely wire this to your DSLR you need a "safe sync"

    Peter - Great idea. Thanks for sharing this info. Why did you add a diode? Where did you put it and what did you wire it to? I assume you wired it to the red LED?

  6. Well, I am repurposing this device as a cheaper way to trigger the camera. If I wanted to spend any more than about $6, I would just buy a trigger, or make one myself. Since I am very sick and have cancer, my funds are extremely limited right now, so repurposing inexpensive items is the way to go for me...

    I have a diode wired in sieres with the positive terminal coming from the L.E.D. and it is reading .03v when the L.E.D. is on, I am assuming that three-hundreths of a volt is an acceptable amount to push into the remote port on the camera. I also replaced the I.R. receiving diode that comes with the unit with a proper laser receiving diode and it works perfectly. Having said that, I did find an alternate laser source, and it would trigger the unit with the supplied I.R. diode in place, but it was intermittent, so I thought replacing the unit was the best course of action.

    Thanks for the idea. Now I just have to wait for the camera connector to arrive... Only the D5000 and D90 use the same connector, which was not terribly difficult to find for a low price.

  7. Does anyone have a drawing or photographs of how it's supposed to be done?
    I'm totally a-technical, but I liked the idea so much I bought one of these things too.
    Now I'm looking at it and feel really stupid...

    Help is much appreciated.